The present invention relates to high speed, melt spinning of polymeric filaments. More specifically, the present invention relates to high speed, melt spinning of polymeric filaments in which tensioning rollers between the extrusion and winding stages are eliminated.
Melt spinning of polymeric filaments to produce strands, yarns or threads from a plurality of such filaments is well known in the art. Generally, in such processes, molten polymer is extruded through a spinneret head having a plurality of extrusion dies. A single die head or spinneret produces a plurality of individual filaments commonly referred to as a threadline of filaments. The threadline of filaments then passes through a quenching chamber wherein the filaments are cooled by forcing air through the chamber normal to the direction of filament travel in order to cure or harden the filaments. Following the quenching of the threadline of filaments, the threadline of filaments is converged to form a single strand, yarn or thread therefrom. The nature and location of this point of convergence varies widely in the art. However, normally the threadline of filaments passes through a convergence guide or over a roller where partial convergence of the threadline of filaments occurs. The partially converged threadline then normally passes through an interfloor guide or tube to a finish applicator where finish is applied to the threadline and thence to godet rolls where the threadlines are wrapped around one or more godet rolls to reduce the tension on the threadlines to a value at which a winding apparatus can effectively operate. Unless the tension is thus reduced, serious problems are encountered during the winding operation, due to the breaking of the filaments, poor winding or the like. Complete convergence of the threadline of filaments to form a single strand quite often takes place either at or adjacent the godet rolls or at the traverse guide which is utilized to spread the threadline across the spindle of the winding apparatus. In this conventional type of melt spinning, winding take-up speeds of less than about 1800 meters per minute are utilized. Thereafter, the wound strand or yarn is drawn by means of draw rollers, to a length about 3 to 4 times its original length. The conventional melt spinning technique generally produces strands which are referred to in the art as a "non-oriented yarn" or withdrawn yarn, hence the necessity of the radical drawing and usually a subsequent texturing operation.
It is also known in the art to melt spin polymeric filaments while utilizing high speeds above about 1800 meters per minute during the winding operation. In this case, the resultant yarns are referred to as "partially oriented yarns (POY)" or partially drawn yarns, primarily to distinguish these yarns from the so-called non-oriented yarns. Such high speed spinning produces a yarn for subsequent treatment in what is known as a draw texturing operation. In draw texturing the yarn is drawn and given a false twist texture in a single operation without intermediate winding. Draw texturing can be sequential, in which the drawing rolls are upstream of the twisting spindle, or simultaneous, in which the drawing is done through the twisting zone. In any event, the drawing in this case is only 1 to 2 times the original length, due to the fact that the yarn is already partially oriented. Normally, in high speed spinning, the threadlines converge at a roll or rollers at the bottom of the quench cabinet then pass through an interfloor tube carrying a plurality of threadlines in a single tube. The threadlines are then wrapped around one or more godet rollers to reduce the tension and are thereafter fed around one or more winders or to a draw texturing means. The problem in this operation is that when one threadline breaks, then all threadlines, passing through a single quench cabinet, through a single interfloor tube and about a single set of godets, have to be broken out and restrung. Usually for threadlines pass through a single quench zone and through a single interfloor tube, thus greatly exaggerating the problem. Obviously, this interrupts normal operations, requires substantial expenditures of labor and is quite inefficient overall. High speed spinning also exaggerates the problem of threadline breakage, since the tension at the godet rolls is normally about 100 grams, due to the fact that the filaments of unconverged yarn experience high air drag passing through the quench chamber, and the godets must reduce this tension to about 25 grams.
It would be highly desirable if the number of threadlines processed in high speed melt spinning could be substantially increased. For example, doubling the number of threadlines per spinneret and the number of threadlines per quench column and interfloor tube would substantially improve the throughput of the spinning apparatus. However, having, for example, eight threadlines per quench column and eight threadlines per interfloor tube would create insurmountable operational problems (i.e., if one threadline breaks, normally all eight threadlines would break or would have to be broken in order to restring the one broken line). This problem would be greatly accentuated if godet rollers are used. At some point all eight strands have to pass over the godet rollers and when any one end breaks out, all or most of the other ends will break out, thus restringing of the godet rolls would be an extremely time consuming, laborious and inefficient operation.
It is therefore an object of the present invention to provide a method and apparatus for melt spinning of polymeric filaments wherein the rate of production is substantially improved. Another object of the present invention is to provide an improved method and apparatus for high speed melt spinning of polymeric filaments which is highly efficient in its use of equipment, space, time and labor. These and other objects of the present invention will be apparent to one skilled in the art from the following description of the present invention.